Combine flour, cheese, lemon peel, thyme, salt and pepper in a food processor. Pulse until combined. Add butter and pulse until mixture resembles cornmeal. Add sour cream and egg yolk. Pulse just until dough comes together.

Transfer dough to lightly floured surface. Gather dough and form into a 12-inch-long log. Wrap with plastic wrap. Chill for at least 2 hours and up to two days. Can also be frozen.

Preheat oven to 375°. Line 2 heavy, large baking sheets with parchment paper. Slice log into 1/4-inch-thick slices. Arrange slices onto baking sheets. Bake until the edges are golden brown, about 20 minutes. Transfer baked crackers onto a plate and serve.

Yield: 40 crackers
Prep time: 15 minutes
Inactive prep time: 2 hours
Cook time: 20 minutes